Pressurization system

ABSTRACT

A pressurization system for supplying a constant pressure source including a liquid propellant source, a reaction chamber for disposing the liquid propellant into a gasified product, a storage tank for storing the gasified products and a feedback system for maintaining the output pressure from the storage tank.

United States Patent De Mattia, Jr. et al. 51 June 6, 1972 lPRESSURIZATION SYSTEM [56] References Cited [72] Inventors: Victor A. DeMattie, Jr., East Long- N TED TATE PATENTS meadow, Mass; Vincent J.Sansevero, Jr., 2 958 193 [1960 Prince 60/39 48 East Hmfmd 3,015,210 m962 Williamson [73] Assignee: United Aircraft Corporation, East Harp3,170,290 2/1965 Porter ..60/39 48 ford, Conn. 3,456,440 7/1969 Keller..60/39.48

[22] Filed: Sept 1968 Primary Examiner-Douglas Hart 2 APPLNQ; 7 3 22Attorney-James A. Kane ABSTRACT 52 U.S.Cl ..60/37, 23/281,23/282,

60/3948 1337/2) A pressurlzatlon system for supplylng a constantpressure 51 1 I I "(106d 5/04 source including a liquid propellantsource, a reaction 58 Field of Search ..60/39.48, 37, 35; 137/209,chamber disP'lsing the liquid pmpe"avnt gasified product, a storage tankfor storing the gasified products and a feedback system for maintainingthe output pressure from the storage tank.

3 Claims, 3 Drawing Figures PATENTEnJuu 5 I972 3.667, 216

sum 20F 2 F/& Z

PRESSURIZATION- SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to a gas generator system and more specifically to a systemwhich provides a predetermined volume of pressurized gas which may beutilized as a constant pressure source.

In the conventional prior art systems whenever gas or a constantpressure source is to be provided, a major difficulty encountered is thenecessity of supplying gas under pressure to the propellant fluidstorage tanks to furnish the necessary fluid supply pressure. Anauxiliary gas supply is generally employed and this therefore requiresthe use of high pressure containers of considerable weight and bulk.This is quite disadvantageous particularly when spaced and weight are ata premium, such as in missile and space vehicles.

Another major disadvantage of these prior art systems is the relativecomplexity of the systems. For example, these systems employ separatesupply storage tanks, piping and pressurant chambers as opposed to thepresent invention single pressurant chamber which contains the liquidpropellant. Additionally, in the construction of the present invention,when the supply in the pressurant chamber is exhausted, it may bereplenished by simply refilling the chamber or inserting a full chamberand discarding the old. Since the supply liquid does not have to bestored under pressure it can be of a relatively lightweightconstruction.

Another major problem with the prior art systems is that normally thesystems are not self-regulated and in the ones that are, self-regulationis achieved in the rather unsatisfactory manner of controlling thesupply pressure of the liquid propellant. These latter constructionstherefore only control the output pressure indirectly. Self-regulationachieved through regulation of the supply pressure and hence indirectlycontrolling the output pressure is undesirable in that the supplypressure remains constant for a given load only and only if that loadremains constant throughout the entire operating cycle. The presentinvention not only provides self-regulation, but maintains a constantpressure on some variable demand load. More specifically, it willmaintain a constant degree of pressurization on the system load within avery tight tolerance band at an infinite variety of flow rates from thepressurized load from zero flow up to the maximum capacity of thesystem.

SUMMARY OF THE INVENTION It is a primary object of this invention toprovide a pressurization system which provides a constant source ofpressure which is relatively lightweight and uncomplex, the system beinga self-regulating one and providing this constant pressure even whenthere is a variable demand load.

The present invention accomplishes the foregoing object by utilizing apressurant chamber which contains a liquid propellant. The chambercontains means for accepting an external signal which initiates thepressurization process. Once the external signal is applied the systembecomes self-sustaining as this signal acts on pressure responsive meanscontained in the chamber. These pressure responsive means in turn act onthe liquid propellant and cause the pressure thereof to rise. Downstreamof the pressurant chamber is a sealing means which prevents the liquidpropellant from exiting from thepressurant chamber until the pressure ofthe liquid propellant reaches a predetermined level.

Once the pressure of the liquid propellant has reached thispredetermined level, it flows through the sealing means and then into areaction chamber where the liquid propellant decomposes and produces agasified product. Positioned downstream of the reaction chamber and incommunication with the outlet of the reaction chamber is a storage tank.The gasified products from the reaction chamber flow into the storagetank and either the gasified products or some other source within thestorage tank may be utilized as the constant pressure source.

self-regulating. system, oneembodiment of this invention, employs afeedback system between the storage tank and the pressurant chamber.This feedback system includes pressure responsive means which permit thegasified. products within the storage tank to pressurize and charge thepressurant chamber and its pressure responsive, means. The feedbacksystem also includes bleed means positioned between the storage tankand: pressurant chamber so that when the pressure rises to apredetermined level, substantially all the flow is diverted from. thepressurant chamber thereby causing the pressure to decrease and causethe pressure in the storage tank to return to the desired constantpressure level. This occurs irrespective of the demand load and withoutregard to whether this load is constant or varying.

In a second embodiment of this invention a control valve is positionedupstream of the reaction chamber. This regulator is simultaneously apressure responsive and a flow-regulating device. More specifically, theregulator meters flow from the pressurant chamber to the reactionchamber as. a function of the pressure within the storage tank, and ischaracterized by moving to the full open or full closed position uponinitiating movement and at a parn'cularly fast rate.

The embodiments of the invention described herein have a number ofadvantages, e.g., they provide a gas generating constant pressure sourcewith zero presure storage capability;

they provide a gas generating means which is simple and which is capableof being relatively insensitive to varying load or operating demandcharacteristics.

BRIEF DESCRIPTION OF- TI-[E DRAWINGS FIG. 1 is a schematic showing o fagas generating means incorporating the device of the invention.

FIG. 2 is a schematic showing of a second gas generating systemincorporating the device of the invention.

FIG. 3 is a fragmentary sectional view of the control valve.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to understand clearlythe nature of the invention and the best means of carrying it out,reference will now be made to the drawings. The gas generating systemillustrated in FIG. 1 includes a housing 2 which incloses pressurantchamber 4. Positioned therein are pressure responsive means 6 hereinillustrated as piston 8 and propellant bellows 10.

The gas generator system is activated by applying an external signal. Inthe present embodiment a pyrotechnic squib 12 is employed, squib l2pressurizing chamber 4 with pressurized gas. The resulting pressureforce acting on upper surface 14 of piston Scauses bellows 10 tocompress against a charge of liquid propellant 16. An acceptable liquidpropellant has been found to be hydrazine and when thehydrazinepropellant 16 reaches a predetermined pressure, sealing means18, which is responsive to pressure, permits the hydrazine to flow intoreaction chamber 20. A pressure responsive sealing means may beemployed, a burst-disc 22 and injector 24 having been found to be anacceptable configuration.

Liquid hydrazine l6 entering reaction chamber 20 then undergoescatalytic or thermal decomposition to produce gasified products. Thegaseous output from the reaction chamber 20 then enters storage tank 30through a reaction chamber outlet 26 where it is pressurized, stored andavailable on demand through outlet 28. It is to be understood that theconstant pressure source may be either the gasified products or a liquidsupply on which the gasified products act or exert a pressure.

Positioned between the storage tank 30 and pressurant chamber 4 andproviding communication therebetween is a feedback system, indicatedgenerally by the reference character 40. Feedback system'40 includesconduit 42 and conduit 44 through which the pressure in storage tank 30is transmitted to pressurant chamber 4. Positioned between storage tank30 and pressurant chamber 4 is -a pressure responsive means 46 hereinillustrated as a burst disc. Therefore, before the pressure in storagetank 30 can be transmitted to pressurant chamber 4, the pressure has torise to a predetermined level and rupture burst disc 46.Once the dischas been ruptured the pressure in tank 30 is transmitted to pressurantchamber 4 and sustains the pressure therein.

Also included in feedback system 40 is duct 48 and upstream therefrompressure responsive means 50. Pressure responsive means as hereinillustrated is bellows 52 which when it expands or contracts, acts onpivotally mounted flapper valve 54. Flapper valve 54 in turn acts as anopening andclosing means for nozzle 56. Nozzle 56 is a bleed means andis positioned in duct or conduit 48. To illustrate the operation of thisparticular portion of feedback system 40, it should be noted that duringthe preliminary charging function of storage tank 30, gaseous productsflow through duct 48 because bellows 52 hold flapper valve 54 tightagainst nozzle 56. However, when the pressure in storage tank 30increases to a predetermined level, bellows 52 cause flapper valve54 topivot and open nozzle 56, thus initiating the pressure regulatingfunction of the gas generating system. Further, when the pressure ismaintained at a predetermined value, the entire flow of gas throughconduit 42 and restriction 58 therein enters duct 48 and is vented toatmosphere through nozzle 56.

If the pressure in storage tank 30 was to rise above the setpredetermined value, bellows 52 would immediately increase the flow areaof nozzle 56 through movement of flapper valve 54, and cause a pressuredrop in conduits 44 and 48. The pressure drop in duct 44 would initiatea flow out of pressurant chamber 4 which would reduce the pressure inchamber 4 and decrease the propellantsupply flow entering reactionchamber 20. This causes the activity within the reaction chamber to fallto a predetermined minimal level while the pressure in storage tank 30slowly bleeds down to the set predetermined level. The'small gaseousdischarge flowing through duct 42 and restriction 56 remains almostconstant regardless of pressure excursions above the minimal set valuein storage tank 30 because the percentage change in pressure drop acrossrestriction 56 remains small.

If the pressure in storage tank 30 were to fall below the minimal setvalue, bellows 52 would immediately close the flow area of nozzle 56.This would permit the entire gaseous 'discharge to enter pressurantchamber 4, thus increasing the pressure force of piston 8. Accordingly,this increases the activity within the reaction chamber in an endeavorto augment the pressure in storage tank 30 to normal levels.

j FIG. 2 is a second embodiment of the present invention and depicts aschematic for a system that controls the output pressure of a liquidpropellant gas generator by metering the flow of propellant. FIG. 3illustrates a control valve which permits performing this function.

The system in FIG. 2 is basically the same system described in FIG. 1.More specifically, the system in FIG. 2 includes a pressurant chamber104, housing 102, pressure responsive means 106 and liquid propellant116. Positioned downstream of chamber 104 is reaction chamber 120 anddownstream therefrom is storage tank 130. Both the reaction chamber 120and storage tank 130 are of similar constructions as chamber 20 and tank30 of FIG. 1 and perform the same functions.

In the system illustrated in FIG. 2, a control valve 140 is positioneddownstream of pressurant chamber 104 and upstream of reaction chamber120. This control valve is more clearly described in FIG. 3 andcomprises a two-stage valve, a

i pressure regulator and a flow regulator. As shown, the input to tion142 and the clearance between the outlet of this port and the meteringface 156 ofv spool 152. A steady-state regulated pressure is maintainedby spring 158 which provides the biasing effect and the proportionalcharacteristics of the regulated output pressures.

Flow regulating valve 144 assumes a stable position only at the extremesof its stroke. Flow regulating valve 144 includes valve spool 162 and asillustrated in FIG. 3, one end 161 of valve spool 162 is positionedwithin chamber 164. As shown, valve spool 162 is in its open position sothat metered propellant flow from duct or port 146 is permitted to flowpast metering edge 166 and into duct 168 unimpeded. Duct 168 is actuallythe outlet of the control valve and any flow issuing therefrom wouldflow into reaction chamber 120, and, additionally is in communicationwith chamber 164.

Valve spool 162 also includes a large piston-like surface 171 positionedin chamber 172 which is the distal end from end 161. Piston surface 171is acted on on one side by spring 174, the spring tending to exert anopening force on valve spool 162. Acting on the opposite side of pistonsurface 171 is the pressure storage tank 130. This occurs since chamber172 is in communication with storage tank by means of duct 176. Itshould be noted that the pressure in storage tank 130 is substantiallythe output pressure from reaction chamber 120. Chamber 172 also includesstop means 178. which physically limits the stroke of valve spool 162 inthe opening direction. It is pointed out that the pressure in chamber164 and spring 174 are substantially the basic forces tending to movethe valve spool in an opening direction and that the pressure in chamber172 is the sole force tending to cause valve spool 162 to move in aclosing direction. More specifically, when the pressure in storage tank130 increases to a predetennined value, this pressure is transmitted tochamber 172 and sets valve spool 162 into motion. As mentionedhereinbefore, movement of valve spool 162 is resisted by two forces, thepressure force in chamber 164 and the force of the spring 174. However,it is the relative change in these forces which affects the primarymotion of the valve spool 162. The force exerted by spring 174 increasesbecause of the compressive effort of the motion of valve spool 162. Themotion of the valve spool 162 also decreases the pressure force inchamber 164 because of the flow of liquid propellant, restrictingeffects of the metering edge 166 which has now partially closed off theexit of duct 146. However, the pressure force in chamber 164 decreasesinordinately compared'to the force increase from spring 174, thusforcing the valve spool 162 to complete the closing stroke very rapidly.In the stroked position, metering edge 166 completely covers duct 146preventing all propellant from entering. The lack of propellant causesthe reaction chamber process to recede, thus allowing the pressure forcein storage tank 130 to remain constant or decrease according to thesystem demand flow.

It should be clear that the flow regulating portion of the control valveis such that the only position in which it is stable is at eitherextreme of its stroke, more specifically, the full open or full closedposition and that the opposing forces are so arranged that when thespool valve begins to move, it completes its stroke very rapidly.Additionally, it should be clear that the single variable pressure.force that causes the spool valve to change its position is the storagetank pressure which is transmitted to chamber 172. When this pressurerises to a predetermined level, it causes the valve to cut off flow andwhen the pressure in chamber 172 decreases to a predetermined level, thespool valve isopen to permit flow of liquid propellant.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described butmay be used in other wayswithout departure from its spirit as defined by the following claims.

We claim:

1. A pressurization system for supplying a constant source of pressurecomprising:

a pressurant chamber including an outlet therefrom, the

chamber including means for receiving an external actuation signal, thechamber having means responsive to the external actuation signal andcontaining a liquid propellant charge, these means pressurizing theliquid propellant and causing the liquid propellant to flow out of thepressurant chamber,

a reaction chamber downstream of the pressurant chamber containing meansof decomposing the liquid propellant and producing a gasified product,

storage tank downstream of the reaction chamber for receiving thegasified products from the reaction chamber,

a control valve positioned between the pressurant chamber and thereaction chamber, the control valve being in a closed position when thepressure level remains at a constant predetermined level,

said control valve being a two-stage regulator, the first of 2. Apressurization system as in claim 1 wherein:

the flow regulating device includes a valve spool, the valve spoolhaving means for opening and closing its inlet and outlet, a firstchamber downstream of the outlet, the chamber being in communicationwith the outlet means and one end of the valve spool, the pressurewithin this chamber being substantially regulated pressure from thefirst stage, a second chamber within which a piston means is positioned,the piston means being connected to the valve spool, a biasing meanspositioned on one side of the piston, the biasing means tending to exertan opening force on the piston and hence open the valve spool inlet, andthe chamber side opposite thereto containing stop means and being incommunication with the storage tank, the pressure therewithin exerting aclosing force on the piston means.

3. A pressurization system as in claim 2 wherein: the valve spool is ina stable position at the extremes of its stroke only, the first chamberpressure force and biasing force being such as to cause the spool valveto move from one end of its stroke to another when the storage tankpressure decays, and the pressure within the second chamber being suchas to cause the spool valve to travel to its other extreme strokeposition when the storage tank pressure increases to a predeterminedlevel.

1. A pressurization system for supplying a constant source of pressurecomprising: a pressurant chamber including an outlet therefrom, thechamber including means for receiving an external actuation signal, thechamber having means responsive to the external actuation signal andcontaining a liquid propellant charge, these means pressurizing theliquid propellant and causing the liquid propellant to flow out of thepressurant chamber, a reaction chamber downstream of the pressurantchamber containing means of decomposing the liquid propellant andproducing a gasified product, a storage tank downstream of the reactionchamber for receiving the gasified products from the reaction chamber, acontrol valve positioned between the pressurant chamber and the reactionchamber, the control valve being in a closed position when the pressurelevel remains at a constant predetermined level, said control valvebeing a two-stage regulator, the first of said stages receiving an inputpressure signal from the propellant leaving the pressurant chamber, thesecond of said stages receiving pressurized liquid propellant from thefirst stage for regulating the flow to the reaction chamber, said secondstage having means to permit the liquid propellant to flow therefrom inresponse to a pressure signal received from the storage tank.
 2. Apressurization system as in claim 1 wherein: the flow regulating deviceincludes a valve spool, the valve spool having means for opening andclosing its inlet and outlet, a first chamber downstream of the outlet,the chamber being in communication with the outlet means and one end ofthe valve spool, the pressure within this chamber being substantiallyregulated pressure from the first stage, a second chamber within which apiston means is positioned, the piston means being connected to thevalve spool, a biasing means positioned on one side of the piston, thebiasing means tending to exert an opening force on the piston and henceopen the valve spool inlet, and the chamber side opposite theretocontaining stop means and being in communication with the storage tank,the pressure therewithin exerting a closing force on the piston means.3. A pressurization system as in claim 2 wherein: the valve spool is ina stable position at the extremes of its stroke only, the first chamberpressure force and biasing force being such as to cause the spool valveto move from one end of its stroke to another when the storage tankpressure decays, and the pressure within the second chamber being suchas to cause the spool valve to travel to its other extreme strokeposition when the storage tank pressure Increases to a predeterminedlevel.